Step 1: Genital warts (condyloma acuminata) are soft growths on the genital and perianal skin, transmitted sexually.
Step 2: They are caused by specific strains of human papillomavirus (HPV), classically the low-risk types HPV-6 and HPV-11, which drive benign warty growth and can cause pain, discomfort, and itching.
Step 3: The distractors cause different diseases: herpes simplex (a) causes genital herpes (painful ulcers/vesicles), cytomegalovirus (c) causes CMV disease in the immunosuppressed, and varicella zoster (d) causes chickenpox and shingles - none produce genital warts.
Step 4: Therefore the causative virus is (b) Human papillomavirus.